Tensed as assembly agreed (8)
I believe the answer is:
assented
'agreed' is the definition.
(assenting is a kind of agreeing)
'tensed as assembly' is the wordplay.
'assembly' indicates anagramming the letters.
'tensed'+'as'='tensedas'
'tensedas' with letters rearranged gives 'ASSENTED'.
(Other definitions for assented that I've seen before include "Expressed agreement" , "Acquiesced" , "Consented" , "Agreed to do something" , "Given agreement" .)